NXP Semiconductors PCA9549PW,118

Overview

The PCA9549PW,118 from NXP Semiconductors is an octal I²C-bus controlled TTL-compatible bus switch IC used for dynamic I²C signal routing in multi-master or multi-peripheral systems. It provides eight independent bidirectional A↔B channels with 5 Ω typical ON-state resistance, supports 0–400 kHz I²C clock rates, operates from 2.3 V to 5.5 V, and features active-low RESET for bus fault recovery.

For engineers reviewing the PCA9549PW,118 datasheet, PCA9549PW,118 pinout, PCA9549PW,118 application, or PCA9549PW,118 equivalent, this device serves as a low-latency, hot-insertion-capable I²C multiplexer/demultiplexer for server management, embedded instrumentation, and modular system architectures requiring isolated peripheral addressing and voltage-level flexibility.

Technical Context

The PCA9549PW,118 implements CBT (Cross Bar Technology) pass-gate switching controlled via an 8-bit I²C-accessible control register. Each bit independently enables or disables one of eight A↔B channel pairs, allowing arbitrary combinations of concurrent connections without propagation delay accumulation.

Its internal state machine includes hardware reset (RESET pin) and power-on reset (POR), both forcing all channels into high-impedance open state. Address pins A0–A2 support up to eight devices on a shared I²C bus, while 5 V-tolerant inputs and Vo(sw) clamping enable mixed-voltage domain bridging (e.g., 5 V master ↔ 3.3 V/2.7 V slaves).

Key Specifications

Pinout & Package

TSSOP24 package (SOT355-1): plastic thin shrink small outline, 24 leads, body width 4.4 mm, lead pitch 0.65 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C bus switching applications.

Compared with TCA9548APWR and PCA9544APW, the PCA9549PW,118 uniquely combines full 8-channel routing, hardware RESET, and 5 V tolerance in a single TSSOP24 package-making it optimal for fault-critical, mixed-voltage I²C infrastructure where bus resilience and scalability are prioritized.

Availability

The PCA9549PW,118 is available at Aetrix Electronics and suitable for server management, industrial sensor hubs, and modular test equipment requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PCA9549PW,118 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA9549PW,118 belongs to NXP's I²C-bus switch and multiplexer product line, designed specifically to solve bus contention, address collision, and voltage-domain interoperability challenges in complex embedded systems.

FAQ

What is the maximum I²C clock frequency supported by the PCA9549PW,118?

The PCA9549PW,118 supports Fast-mode I²C operation up to 400 kHz, as confirmed in its dynamic characteristics table. Its low 5 Ω ON-state resistance and ≤5 pF I/O capacitance preserve signal integrity at this rate, enabling reliable high-speed peripheral enumeration and configuration without added timing margin constraints in the PCA9549PW,118 design.

Does the PCA9549PW,118 require external pull-up resistors on SDA and SCL lines?

Yes, the PCA9549PW,118 requires external pull-up resistors on both SDA and SCL lines, as specified in Section 7 of the datasheet. Its I²C interface uses open-drain outputs, and proper bus termination is essential for meeting rise-time requirements-especially critical at 400 kHz operation. The PCA9549PW,118 itself does not integrate internal pull-ups.

Can the PCA9549PW,118 be used for voltage level translation between 5 V and 3.3 V I²C buses?

Yes, the PCA9549PW,118 supports voltage translation via its Vo(sw) clamping behavior: when powered at 3.3 V, Vo(sw) remains ≤2.7 V, safely limiting downstream bus voltage. This allows a 5 V master to communicate with 3.3 V peripherals through the PCA9549PW,118 without additional level-shifting components.

How does the RESET pin function on the PCA9549PW,118?

The RESET pin on the PCA9549PW,118 is active-low and forces all eight channels into high-impedance open state while resetting the internal I²C state machine. A minimum 4 ns LOW pulse clears the control register, recovering from stuck-bus conditions. The PCA9549PW,118 requires an external pull-up resistor on RESET to ensure normal operation after power-up.

Is the PCA9549PW,118 compatible with SMBus protocols?

Yes, the PCA9549PW,118 is explicitly stated to be I²C-bus interface logic compatible with SMBus standards. Its timing parameters (tHD;STA, tSU;DAT, etc.), voltage thresholds (VIH/VIL), and functional behavior-including timeout handling via RESET-align with SMBus 2.0 specifications, making the PCA9549PW,118 suitable for system management applications in servers and telecom equipment.